Fluid filtration using splines

ABSTRACT

A method for filtering a fluid that includes collecting contaminates in the fluid, passing the fluid from inside an internal cavity of a first shaft through a tight clearance at a spline connection between the first shaft and a second shaft such that the fluid is filtered of contaminates as a result of the tight clearance, and delivering the filtered fluid to a delivery location.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. application Ser. No. 14/199,483filed Mar. 6, 2014, for “Fluid Filtration Using Splines” by Steven AHeitz and Keith E. Short.

BACKGROUND

The presently disclosed embodiments generally relate to an apparatus andmethod for filtering contaminates from a fluid.

In one example, an engine uses a fluid, such as oil, to providelubrication between contacting surfaces. The lubrication acts as a filmseparating the two contacting surfaces, and thus helps with coolingwhile preventing or minimizing metal fatigue, wear, and excessive heatcaused by friction. However, during manufacture, installation, operationand/or repair of engine components, various contaminates mayinadvertently be entrained in the engine. Such contaminates can includemanufacturing debris (such as metal shavings), machining chips, and weardebris. These contaminates can be difficult to inspect for and removefrom the engine, as they often are found in relatively small,inaccessible internal passages of the engine. As a result, when oil ispassed over or through engine components these contaminates may becomeentrained into the oil, which is problematic when this oil is then laterdelivered to provide lubrication to various other engine components.Specifically, contaminates within the oil can cause damage and evenfailure to the components receiving the fluid as lubrication.

Therefore, to help ensure components needing lubrication are not damagedand do not fail, the oil should be free of damaging contaminates whendelivered. Various prior solutions have included using a separatelyrouted and isolated oil supply, which can be kept free of contaminates,to provide lubrication. However, use of a separate oil supply requiresnew, additional parts, such as oil passages and reservoirs whichincrease the weight and both the cost of manufacturing and maintainingthe engine. Another prior solution has included installing additionalstructures within the engine to collect and trap contaminates within theoil. However, installing additional structures again requires addingnew, additional parts increasing weight and cost.

SUMMARY

One embodiment of the present invention includes an assembly forfiltering a fluid. The assembly includes a first rotatable shaft with afirst set of splines. The first rotatable shaft has an internal cavitycontaining the fluid. Also included is a second rotatable shaft with asecond set of splines mated to the first set of splines. The secondrotatable shaft includes at least a portion of a supply hole. The firstrotatable shaft and the second rotatable shaft are configured to conveythe fluid from the internal cavity through a tight clearance between thefirst set of splines and the second set of splines, to filter the fluid,and then out the supply hole.

Another embodiment includes a method for filtering a fluid. The methodincludes collecting contaminates in the fluid. The fluid is passed frominside an internal cavity of a first shaft through a tight clearance ata spline connection between the first shaft and a second shaft, suchthat the fluid is filtered of contaminates as a result of the tightclearance. The filtered fluid is delivered to a delivery location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an embodiment of a shaft assemblywith a spline connection.

FIG. 2 is an enlarged cross-sectional view of the spline connection,taken along line 2-2 of FIG. 1.

FIG. 3 is a flow chart illustrating an embodiment of a method offiltering a fluid.

While the above-identified drawing figures set forth one or moreembodiments of the invention, other embodiments are also contemplated.In all cases, this disclosure presents the invention by way ofrepresentation and not limitation. It should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art, which fall within the scope and spirit of the principles of theinvention. The figures may not be drawn to scale, and applications andembodiments of the present invention may include features and componentsnot specifically shown in the drawings.

DETAILED DESCRIPTION

Generally, the present embodiments provide a fluid filtered ofcontaminates that have become entrained in the fluid in order to helpprevent damage to, and/or failure of, components to which the fluid isdelivered, such as bearings. The fluid is filtered through a combinationof both centrifugal forces and by passing the fluid through a splineconnection with a tight clearance between mated splines. Contaminatesthat have become entrained in the fluid are prevented from passingthrough the tight clearance, which is too small for the contaminates topass through but large enough for the fluid to pass through. After thefluid has been passed through the tight clearance, it can be deliveredto a component to provide lubrication without risk that the lubricatedcomponent will be damaged. Significantly, the filtering of the fluid canbe accomplished without requiring new, additional parts and/or using aseparately routed filtered oil supply.

FIG. 1 is a cross-sectional view of an embodiment of shaft assembly 10.Assembly 10 includes first shaft 12, cavity 14, first set of splines 16,second shaft 18, cavity 20, second set of splines 22, fluid 26(represented by arrows), contaminates 27, spline undercut 30, supplyhole 32, 360° groove 34, bearing spacer 36, hole 38, bearings 40, andcenterline A.

First shaft 12 includes cavity 14 and first set of splines 16. Secondshaft 18 includes cavity 20 and second set of splines 22. First set ofsplines 16 is mated to second set of splines 22 (forming splineconnection 48, described below with respect to FIG. 2). Mating first setof splines 16 with second set of splines 22 provides a non-rotatableconnection between first shaft 12 and second shaft 18, such thatrotating shaft 12 or 18 causes the other shaft 12 or 18 to also rotate.In other words, splines 16 and 22 rotationally fix shafts 12 and 18relative to each other.

Fluid 26 is supplied by a jet (not shown) at approximately atmosphericpressure into cavity 20 of second shaft 18, and flows into cavity 14 offirst shaft 12 as a result of a fluid connection between cavities 14 and20. Fluid 26 can be, for example, oil. Fluid 26 stays at substantiallyatmospheric pressure while passing through assembly 10. Contaminates 27may include, for example, manufacturing debris (for instance, metalshavings), machining chips, and/or wear debris. Spline undercut 30 is adepression of an interior surface of second shaft 18 near an end ofsecond shaft 18 and adjacent to second set of splines 22. Supply hole 32is a conduit which runs through second set of splines 22 on one end andextends to groove 34 on another end. Groove 34 is a circumferential,360° groove in second shaft 18. Groove 34 is sized such that groove 34is thinner (shorter width longitudinally with respect to centerline A)than bearing spacer 36, to prevent bearing spacer 36 from dropping intogroove 34.

Bearing spacer 36 is located between bearings 40 and assists in keepingbearings 40 in intended locations. Hole 38 is located in bearing spacer36 and provides an exit to bearings 40 for fluid 26. In the illustratedembodiment bearing spacer 36 includes one hole 38, but in otherembodiments there could be multiple holes spaced from each other, suchas in a circumferential manner. In embodiments with multiple holes 38,groove 34 may eliminate a need to clock holes 38.

Bearings 40 contact with second shaft 18, providing a substantiallyfriction-free interface and support to second shaft 18, which in turnsupports first shaft 12 (connected to second shaft 18 through matedfirst set of splines 16 and second set of splines 22).

FIG. 2 is a cross-sectional view of a portion of spline connection 48taken along line 2-2 of FIG. 1. Included in FIG. 2, in addition to thatpreviously shown and described, are spline connection 48, spline toothroots 50, spline tooth tips 52, spline tooth roots 54, spline tooth tips56, and tight clearance 58. Spline connection 48 is formed when firstset of splines 16 is mated with second set of splines 22, forming theconnection between first shaft 12 and second shaft 18. First set ofsplines 16 is made up of a series of alternating tooth roots 50 andtooth tips 52. In the illustrated embodiment, first set of splines 16 isan external (i.e., radially outwardly protruding) set of splines onfirst shaft 12. Second set of splines 22 is made up of a series ofalternating tooth roots 54 and tooth tips 56. In the illustratedembodiment, second set of splines 22 is an internal (i.e., radiallyinwardly protruding) set of splines on second shaft 18, however, inother embodiments second set of splines 22 can be an external set ofsplines while first set of splines 16 can be an internal set of splines.Both first set of splines 16 and second set of splines 22 are straightsplines in the illustrated embodiment.

Supply hole 32 extends radially outward from a single tooth tip 56 inthe illustrated embodiment. Supply hole 32 is located axially (withrespect to centerline A) in an approximate middle of spline connection48, such that supply hole 32 is spaced from both ends of splineconnection 48. Here, supply hole 32 is located at a tooth tip 56, andnot a tooth root 54, because tooth roots 54 are closer to the outerperiphery of spline connection 48, where contaminates 27 collect due tocentrifugal forces (described later). However, in other embodiments,supply hole 32 could be located at various locations along splineconnection 48 and multiple supply holes 32 could be included, with theexact number varying depending on the application and/or the size offirst set of splines 16 and second set of splines 22. Clearance 58constitutes the space between a single tooth tip 56 and a single toothroot 50 at spline connection 48. Clearance 58 is the maximum spacingbetween first set of splines 16 and second set of splines 22 at splineconnection 48.

During operation of shaft assembly 10, second shaft 18 rotates, in turnrotating first shaft 12 through spline connection 48. Fluid 26 travelsthrough cavity 20 and enters cavity 14. Cavity 14 begins to fill withfluid 26 until the volume of cavity 14 is filled, or substantiallyfilled, with fluid 26. Fluid 26 then flows from cavity 14 and entersspline undercut 30. Fluid 26 can also enter spline undercut 30 directlyfrom cavity 20. However, as fluid 26 is passed through assembly 10,contaminates 27 may become entrained in fluid 26, which presents a riskof damage to components to which fluid 26 is delivered, such as bearings40. For example, spline undercut 30 often contains contaminates 27 whichare difficult to inspect for and clean out, and as a result thesecontaminates 27 may become entrained in fluid 26 present in splineundercut 30. Contaminates 27 entrained in fluid 26 are carried by fluid26 upstream (i.e., axially, relative to centerline A, before splineconnection 48) from clearance 58.

To help prevent contaminates 27 entrained in fluid 26 from damagingcomponents to which fluid 26 is ultimately delivered, contaminates 27can be filtered out from fluid 26 by shaft assembly 10. After enteringspline undercut 30 as previously described, fluid 26 then passesdownstream into spline connection 48 and is accelerated to therotational speed of shafts 12 and 18. At spline connection 48, fluid 26acts to provide lubrication between first set of splines 16 and secondset of splines 22 at spline connection 48, but at the same time fluid 26is also filtered. The rotation of shafts 12 and 18 creates centrifugalforces which act to push contaminates 27 (which generally have a greatermass than fluid 26) in fluid 26 to an outer periphery of both splineundercut 30 of second shaft 18 and spline connection 48 (the outerperiphery of spline connection 48 being where shaft 18 is located). Thecentrifugal forces also help to keep contaminates 27 at the outerperipheries of both spline undercut 30 and spline connection 48.Additionally, contaminates 27 not forced to the outer peripheries aresubstantially prevented from passing through spline connection 48because of clearance 58.

Tight clearance 58 (shown in FIG. 2), between tooth root 50 of first setof splines 16 and tooth tip 56 of second set of splines 22, acts tofilter contaminates 27 from fluid 26 as fluid 26 passes through splineconnection 48. Clearance 58, is sized such that contaminates 27 thatwould present a risk of damage to components to which fluid 26 isdelivered are prevented from passing through. Thus, clearance 58 is toosmall for contaminates 27 to pass through, but large enough for fluid 26to pass through. Clearance 58 in the illustrated embodiment isapproximately 0.005 inch (0.013 cm). However, in other applicationsclearance 58 can range, for example, from approximately 0.001 inch(0.003 cm) to 0.010 inch (0.025 cm). For instance, where clearance 58 issized at approximately 0.010 inch (0.025 cm) contaminates 27 sizedgreater than approximately 0.010 inch (0.025 cm) will be filtered fromfluid 26. The size of clearance 58 can vary depending on the componentto which fluid 26 is to be delivered, and specifically the size ofcontaminates 27 that can present a risk of damage to componentsreceiving fluid 26.

Consequently, after passing through clearance 58, fluid 26 is filteredand can be substantially free of contaminates 27 when fluid 26 enterssupply hole 32. When filtered fluid 26 enters supply hole 32 at splineconnection 48, the centrifugal action created by rotating shafts 12 and18 acts to pump fluid 26 generally radially outward through supply hole32 to groove 34, and ultimately fluid 26 is ejected out hole 38 anddelivered to bearings 40. The flow rate at which fluid 26 is ejected outholes 38 can be adjusted, for example, by selecting a desired area ofhole 38.

The combination of centrifugal forces and clearance 58 allows fluid 26to be delivered to bearings 40 through supply hole 32 with a relativelylow risk that contaminates 27 in fluid 26 will damage bearings 40.Significantly, assembly 10 uses the same fluid 26 to lubricate bothspline connection 48 and bearings 40.

FIG. 3 is a flow chart illustrating an embodiment of method 70 forfiltering fluid 26. At step 72, first set of splines 16 of first shaft12 is mated to second set of splines 22 of second shaft 18 to formspline connection 48. Spline connection 48 includes tight clearance 58between tooth tip 56 of second set of splines 22 and tooth root 50 offirst set of splines 16. At step 74, contaminates 27 are collected influid 26. Contaminates 27 may be collected in fluid 26 as fluid 26passes through assembly 10. At step 76, fluid 26 with contaminates 27 ispassed through tight clearance 58, which filters fluid 26 ofcontaminates 27 before fluid 26 enters supply hole 32. Step 78 includesdelivering fluid 26 that exits supply hole 32 to a delivery location.Fluid 26 is pumped through supply hole 32 and ultimately ejected out toa desired delivery location. The delivery location may includecomponents that need to receive lubrication, such as bearings 40. As aresult, method 70 filters fluid 26 of contaminates 27 that may causedamage at the delivery location.

Assembly 10 can be utilized to filter fluid 26 in various applications.Such applications can include gearboxes and power transmission devices.

Description of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

An assembly for filtering a fluid, the assembly comprising a firstrotatable shaft with a first set of splines, wherein the first rotatableshaft has an internal cavity containing the fluid; and a secondrotatable shaft with a second set of splines mated to the first set ofsplines, wherein the second rotatable shaft includes at least a portionof a supply hole, and wherein the first rotatable shaft and the secondrotatable shaft are configured to convey the fluid from the internalcavity through a tight clearance between the first set of splines andthe second set of splines, to filter the fluid, and then out the supplyhole.

The assembly of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

The supply hole is positioned at a location where the first set ofsplines and the second set of splines mate.

The supply hole extends radially outward from a tooth tip of the secondset of splines.

Contaminates carried by the fluid upstream from the tight clearancebetween the first set of splines and the second set of splines.

The contaminates collect at a periphery of the mated first set ofsplines and the second set of splines, when the first shaft and thesecond shaft are rotated.

The tight clearance ranges from approximately 0.001 inch (0.003 cm) toapproximately 0.010 inch (0.025 cm).

The tight clearance ranges from approximately 0.004 inch (0.010 cm) toapproximately 0.006 inch (0.015 cm).

The first set of splines and the second set of splines are both straightsplines.

The first set of splines are external splines and the second set ofsplines are internal splines.

A method for filtering a fluid, the method comprising collectingcontaminates in the fluid; passing the fluid from inside an internalcavity of a first shaft through a tight clearance at a spline connectionbetween the first shaft and a second shaft, such that the fluid isfiltered of contaminates as a result of the tight clearance; anddelivering the filtered fluid to a delivery location.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, the following techniques, steps,features and/or configurations:

Directing contaminates to a periphery of the spline connection through acentrifugal action.

Delivering the filtered fluid to the delivery location through a supplyhole in the second shaft.

Delivering the filtered fluid to the delivery location comprisesdelivering the filtered fluid to a bearing.

Maintaining the fluid at approximately atmospheric pressure.

The fluid is filtered of contaminates sized greater than approximately0.010 inch (0.025 cm).

Any relative terms or terms of degree used herein, such as “generally”,“substantially”, “tight” and the like, should be interpreted inaccordance with and subject to any applicable definitions or limitsexpressly stated herein. In all instances, any relative terms or termsof degree used herein should be interpreted to broadly encompass anyrelevant disclosed embodiments as well as such ranges or variations aswould be understood by a person of ordinary skill in the art in view ofthe entirety of the present disclosure, such as to encompass ordinarymanufacturing tolerance variations, incidental alignment variations,temporary alignment or shape variations induced by operationalconditions, and the like.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A method for filtering a fluid, the method comprising: collectingcontaminates in the fluid; passing the fluid from inside an internalcavity of a first shaft through a tight clearance at a spline connectionbetween the first shaft and a second shaft, such that the fluid isfiltered of contaminates as a result of the tight clearance; anddelivering the filtered fluid to a delivery location.
 2. The method ofclaim 1, further comprising directing contaminates to a periphery of thespline connection through a centrifugal action.
 3. The method of claim1, further comprising delivering the filtered fluid to the deliverylocation through a supply hole in the second shaft.
 4. The method ofclaim 1, wherein delivering the filtered fluid to the delivery locationcomprises delivering the filtered fluid to a bearing.
 5. The method ofclaim 1, further comprising maintaining the fluid at approximatelyatmospheric pressure.
 6. The method of claim 1, wherein the fluid isfiltered of contaminates sized greater than approximately 0.010 inch(0.025 cm).